Lithographing process



Patented Mar. 5, 1940 2 PATENT OFFICE m'rnocaarnmo raocass PhilipSchroeder, Cleveland, om, assignor of one-sixth to Lawrence J. Clark,Lakewood, Ohio, and fonr-sixths to Irvin J. Dossman, Cleveland, Ohio- NoDrawing.

Application February I, 1938, $6118! No. 189,213

6 Claims. (01. 101-149) My invention relates generally to the art oflithography and particularly to the offset types of process commonlyemployed therein, and an important object of my invention is to providea procedure applicable to such types of processes and others whereby theuseful life of the etched lithographic plate is increased several times.

Another important object of my invention is to provide procedure of thecharacter indicated whereby the necessity of the steps of gumming andwashing the preparedplate is eliminated.

Another important object of my invention is to provide means whereby theprepared lithographic plate is rendered practically immune to damage byexposure to air, by contact with grease, by scum, and by other agenciesordinarily met with in lithographing- Another important object of myinvention is to provide a prepared lithographic plate which is permanentin character and does not spoil through oxidation or through contactwith or exposure to the usual damaging agencies met with in the courseof conducting a lithographing process or in attempted storage of theplate.

Other important objects and advantages of my invention will be apparentfrom a reading of the following description and example given forillustrative purposes and showing a preferred embodiment of myinvention.

In accordance with the present invention the lithographic plate is putthrough the usual processing up to and including thetransfer of theimage of the photographic negative onto the sensitized linedlithographic plate and the inking thereof. From this point on theprocedure is peculiar to the present invention in that instead ofapplying to the plate the usual etching solution the operator appliesthereto in the usual way, first, a plate solution, and secondly. afountain etch solution, both solutions being peculiar to the presentinvention and cooperative in action to fulfill the objects andadvantages of the invention stated hereinabove.

'I'he fountain etch solution consists of a solution of about'.2 ouncesin one 1) gallon of water of the resultant of a mixture of from l to 8ounces of chrome alum (potassium chrome alum having the formulaCI2(SO4)3.K2SO4.24H2O) from 2 to 6 ounces of phosphoric acid; from ,4 tol ounce of tannic acid; from $4; to 3 lbs. of gum arabic; and one (1)gallon of water.

A preferred form of the fountain .etch solution prior to dilution of 2ounces thereof in the stated one (1) gallon of water consists of theresultant of a mixture of substantially:

The plate solution consists of the undiluted resultant of a mixture offrom 1 to 8 ounces of chrome alum; from 2 to 6 ounces of phosphoricacid; from it to 2 ounces of tannlc acid; from water.

A preferred form of the plate solution consists of the resultant of amixture of substantially:

Chrome alum ounces (by weight) 4 Phosporic acid. do 4 Tannic acid do 1Gum arabic pound (by weight) 1 water gallon (by weight) 1 narilydamaging agencies set forth.

The plate solution gives longer life to the lithographic plate and makesit unnecessary to gum the plate during stops in production. The plate ismade in considerably less time because of the elimination of someoperations now generally used when making the plate.

The present process makes the plate more resistant to scumming and whenthe ink is allowed to pile up during the printing it can be very easilyand positively cleaned off. The present process makes a plate lessliable to destruction to 4 lbs. of gum arabic, and one (1) gallon of bythe usual carelessness and accidents of press! men. The fountain etchsolution makes possible the correction of plates by dot etching.

Although I have set forth and described herein preferred embodiments ofmy invention it is to be definitely understood that I do not desire tolimitthe application of the invention thereto, but any change or changesmay be made in the procedure and in the materials employed, within thespirit of the invention and the scope of the subjoined claims.

Having described the invention, what is claimed as new is:

1. An etched plate fixing solution consisting of the product of amixture of chrome alum, phosphoric acid, tannic acid, gum arabic, andwater.

2. In a process of preparing a metal plate for lithographic printingwhich involves sensitizing the plate, transferring thereto aphotographic image, and inking, the steps of applying to the inkedsurface of the plate a plate solution consisting of a relativelyconcentrated aqueous solution of chrome alum, phosphoric acid, tannicacid and gum arabic and allowing the reaction to proceed, then applyingto the resultant surface of the plate a relatively dilute aqueoussolution of chrome alum, phosphoric acid, tannic acid and gum arabic.

3. In a process of preparing a metal plate for lithographic printing,the said process involving conventional steps of sensitizing the face ofthe plate and applying thereto a photographic image to and inking saidface, the steps of applying to the inked face an undiluted platesolution consisting of the resultant of a mixture of chrome alum,phosphoric acid, tannic acid, gum arabic and water, and allowing thereaction to proceed;

then applying to the resultant face-a relatively dilute fountainsolution consisting of a solution ounces of phosphoric acid, A to 2ounces of tannic acid, to 4 pounds of gum arabic and one gallon of waterand allowing the consequent reaction to proceed then applying to theresultant face of the plate a fountain solution consisting of a solutionin about one gallon of water of about 2 ounces of the resultant of amixture of' 1 to 8 ounces of .chrome alum, 2 to 6 ounces of phosphoricacid, A to 1 ounce of tannic acid, to 3 pounds of gum arabic and onegallon of water.

5. An etching solution of the character described, said etching solutionconsisting of the resultant of a mixture of about 1 to 8 ounces ofchrome alum, from 2 to 6 ounces of phosphoric acid, from ,4, to 2 ouncesof tannic acid, from to 4 pounds of gum arabic and about one gallon ofwater.

,6. An etched plate fixing solution of the character described, saidfixing solution consisting of a solution in about one gallon of water ofabout 2 ounces of the resultant of a mixture of substantially 1 to 8ounces of chrome alum, 2 to 6 ounces of phosphoric acid, to 1 ounce oftannic acid, A to 3 pounds of gum arabic and one gallon of water.

PHILIP SCI-IROEDER.

